The invention relates to a combustion chamber for a turbomachine.
One of the prime objectives in the field of turbomachines used in aeronautics, especially for civil use but also for military use, is the reduction of atmospheric pollution and especially the reduction of the emission of oxides of nitrogen.
The production of oxides of nitrogen depends on the richness of the fuel-air mixture, temperature, compression ratios and length of combustion. It occurs in particular in regions of the combustion chamber in which the richness is close to the stoichiometric ratio and is all the greater, the higher the temperature and compression ratio. It is also advisable for the time of residence in these critical regions to be reduced, or for the size of these regions to be reduced.
The problem is all the more difficult to solve when the aviation turbomachines are subject to different flight speeds, particularly at idling speed and at full throttle speed for aircraft take-off.
French Patent Nos. 2 691 235; 2 706 021 and 2 686 683 propose combustion chambers in which the fuel injectors are split into two groups, the injectous of one of the groups being intended to supply fuel during a first operating mode, such as at idling speed, and the injectors of the other group being intended to supply fuel during a second operating mode, such as at full throttle speed. In these combustion chambers, the two groups of injectors are arranged concentrically in the end of the chamber and are separated by dividing plates which extend towards the inside of the chamber, so as to define two sections of different length in the combustion space, the shorter section being used at full throttle speed. These combustion chambers, known as double-head chambers, are complicated and cumbersome for a given maximum thrust, because the injectors for one of the heads are not operating for part of the flight and during take-off. Furthermore, in this type of chamber, the dividing plates have to withstand very high and often asymmetric mechanical and thermal stresses. They are, for these reasons, difficult to design and to manufacture.
The present invention proposes another solution, which is simpler than the previous ones and has other advantages for reducing the omissions of oxides of nitrogen.